Changing liferea keyboard shortcuts

Liferea has no keyboard shortcut editor itself, but "Toggle unread status" demands the wrist-breaking chord action of Control-U. It expects you to be able to edit the shortcuts via the editable menu feature of GTK+.

Unfortunately that's disabled on all modern GNOME installs, and there's no UI for re-enabling it. As usual, gconf-editor to the rescue. The key you need to change is /desktop/gnome/interface/can_change_accels. After re-starting Liferea, you can then edit via hovering over the menu item and pressing the combination. Of course, this in itself is buggy: if it clashes with a menu accelerator (as 'r' is), it will perform that action instead.

It's simpler to directly edit the accels file in your Liferea dot dir.

Epson all-in-ones: avoid like the plague

Browsing the net, you might get the impression that Epson Stylus All-in-ones are well supported under Linux. Unfortunately this is not the case. The pipslite driver you have to install is extremely flaky, and Fedora SELinux doesn't work properly with it. There's no "draft" mode for some bizarre reason; printing is extremely slow and often randomly cancels half-printed jobs due to USB resets

The scanner doesn't work at all with the iscan software, despite claims to the contrary.

Setting up JACK on Fedora 12

Audacity is somewhat of a broken joke these days, so I needed to use Ardour to record. And that meant setting up JACK. Since JACK insists on exclusivity, I also needed to route pulseaudio through JACK so I could use other apps at the same time. Unfortunately, this is a bit of a pig to figure out. I hacked it as follows:

First edit /etc/pulse/default.pa, you need to add two lines:

load-module module-jack-sink
load-module module-jack-source

In theory now, a restart of pulseaudio should start using JACK for recording and playback, if jackd is running. However, it tends not to work very well: you might find PA hanging and you have to kill -9 it.

This isn't enough of course, now when you log in again, gnome-session will try to start pulseaudio, but not jackd, so nothing works. It's far from the right way, but I edited /usr/bin/start-pulseaudio-x11 (which is started from a /etc/xdg/autostart/ script), as follows:

amixer -c 0 sset 'Input Source' 'Line'

nohup jackd -d alsa &

sleep 5

/usr/bin/pulseaudio --start "$@"

Note that I have to set the input source by hand: something in desktop start up used to do this for me, but now I'm going through JACK it has to be done by hand.

Liferea strict feed validation tip

New versions of Liferea refuse to parse any feed that fails to validate, even for relatively "minor" problems (the libxml2 recovery facility is no longer used; besides, it abandons the rest of the feed when it hits such problems). I don't want to use Google Reader, since I don't like the interface.

Typically bad feeds have things like high-bit chars or bare ampersands. Thankfully, there's a "conversion filter" feature that you can use to work around the bad feeds. On the two bad feeds, I run this filter:

[moz@pent ~]$ cat bin/fix-ampersands 
#!/bin/bash

sed 's/\o226/&/g' | sed 's/& /\&/g' | sed 's/\o243/GBP/g'

The main indicators of egotism as I intend it here are are loud self-display, insecurity, constant approval-seeking, overinflating one’s accomplishments, touchiness about slights, and territorial twitchiness about one’s expertise. My claim is that egotism is a disease of the incapable, and vanishes or nearly vanishes among the super-capable.

I’m the crippled kid who became a black-belt martial artist and teacher of martial artists. I’ve made the New York Times bestseller list as a writer. You can hardly use a browser, a cellphone, or a game console without relying on my code. I’ve been a session musician on two records. I’ve blown up the software industry once, reinvented the hacker culture twice, and am without doubt one of the dozen most famous geeks alive.

No prizes for guessing who this was.

A horrible little ElementTree gotcha

What does this print:

from lxml import etree
doc = etree.fromstring('<a><b><c/></b></a>')
newdoc = etree.ElementTree(doc.find('b'))
print newdoc.xpath('/b/c')[0].xpath('/a')

The answer is: [<Element a at 817548c>]. The first point to note is that xpath() against an element is only relative to that element: any absolute XPaths enumerate from the top of the containing tree. The second point is that the shallow copying of etree means that _Element::xpath, unlike _ElementTree::xpath, evaluates absolute paths from the top of the original underlying tree! So even though there's no <a> in newdoc, an absolute XPath on a child element can still reach it.
Yuck.

YouTube annoyance

How much time would it really take to order multi-part videos, so the suggestion at the end of the video is the next part? Please!

An annoying Python gotcha

Imagine you have this in mod.py:

import foo

class bar(object):
   ...

   def __del__(self):
       foo.cleanup(self.myhandle)

Seems fine right? In fact, there's a nasty bug here. If I try to use this module in client.py like so:

import mod
mybar = bar()

Then you're likely to get an exception when the program exits. This is because Python, for some bizarre reason, Nones out the globals in mod.py when taking down the interpreter. The actual __del__ method can be called sometime after this, and it ends up trying None.cleanup(), with the resultant AttributeError. It seems extremely bizarre that it happens in this order, but it does (a real example).

Kernel solipsism

Thomas Gleixner:

Exactly that's the point. Adding dom0 makes life easier for a group of users who decided to use Xen some time ago, but what Ingo wants is technical improvement of the kernel... The kernel policy always was and still is to accept only those features which have a technical benefit to the code base.

It boggles the mind that someone could get things so backwards. The kernel exists to provide services to the outside world, not the other way around. By all means criticise the details of the Xen dom0 code, but this argument makes zero sense. How precisely did x86_64 support provide a technical benefit to the code base?

BNP

Charlie Brooker on the BNP party political broadcast:

Nick Griffin's first line is "Don't turn it off!", which in terms of opening gambits is about as enticing as hearing someone shout "Try not to be sick!" immediately prior to intercourse.

Outputting XML in standard Python

Is it really this ugly? I expected something like this:

doc = xmldoc()
doc.start('foo', { 'id': 'blah' })
doc.start('sub')
doc.text('subtext')
doc.close('sub')
doc.close('foo')
print doc

and I thought I had it in SimpleXMLWriter. However, I have to jump hoops to get it to output to a string, and it doesn't have any pretty-print. I tried using ElementTree, but that also doesn't pretty print! libxml2 is horribly low-level. lxml seems to do pretty printing, but it's still just as ugly as the best option I've found so far, xml.dom.minidom:

from xml.dom.minidom import Document
foo = doc.createElement('foo')
foo.setAttribute('id', 'blah')
doc.appendChild(foo)
sub = doc.createElement('sub')
sub.appendChild(doc.createTextNode('subtext'))
foo.appendChild(sub)

Yuck! If I'm building up a document, I almost always want to append directly at the last point: why do I have to keep track of all these elements by hand? I presume I'm missing some small standard helper module, but #python didn't know about it. Anyone?

Scoble sets a new record

I really hate the word “friend.” It has no meaning anymore. No one can define what a friend is. Believe me, I’ve asked dozens of people to define it for me. My wife is my most “true” friend, for instance but if you trust her with picking a great wine (she doesn’t drink much) or picking a great sushi restaurant (she hates the stuff) you’ll be very disappointed. You’d be better off asking @garyvee about the wine even though you’ve never met him and he probably wouldn’t be listed among your “true” friends.

- Scoble

Might I gently suggest friendship isn't about wine recommendations?

Sheesh

Apparently applications should be prepared to lose 60 minutes of data to work around the file system now.

Of course the notion that application should have explicit load/save operations is a nonsense already. Now we should "fix" one of the few places that never had this (ever seen a browser where you have to save your bookmarks explicitly when you quit?) to expose this implementation detail in a data-losing way again.

Amazon

It's a shame that it's basically impossible to compete with Amazon when it comes to online book selling, because their website is so horribly awful to use. Not fair.

It's not just atol(), Nicholas

Nicholas Nethercote warns us against atol(). Sadly, he recommends using strtol() instead. This interface is almost as bad. If atol() is impossible to get right, strtol() has to be classified under the obvious use is wrong.

As a perfect example of how horrible strtol() is, let's look at his example code:

int i1 = strtol(s,        &endptr, 0);  if (*endptr != ',')  goto bad;
int i2 = strtol(endptr+1, &endptr, 0);  if (*endptr != ',')  goto bad;
int i3 = strtol(endptr+1, &endptr, 0);  if (*endptr != '\0') goto bad;
...
bad: /* error case */

Can you spot the bug? What about an input like ",2,3" ? Nicholas does mention that this code is broken for underflow or overflow (you must wrap every singe call like this: "errno = 0; strtol(...); if (errno...)") but either missed this or considered it irrelevant. It's just too hard to get right.

Just use the *scanf() family (yes, that's hard to use too). Be suspicious of any code using either strtol() or atol().

Comics I Don't Understand

Comics I Don't Understand. One for Seinfeld fans. What I don't understand is how someone can have a Wordpress design that has no "Previous" button. Blech.

Heston Blumethal's Feasts

I've just watched last week's episode of this series, Heston Blumenthal's Victorian Feast. The guy is the epitome of the mad scientist (his dessert was strawberry, elderflower and absinthe dildo jelly with earl grey ice cream).

I had one of his inventions a while back: strawberry, olive and leather vanilla sundae. It was pretty nice, though the rather more staid chocolate wine popsicle was much nicer.

You should watch Tuesday's...

Tomcat on Centos 5.2: just don't

If you were thinking of trying to use CentOS 5.2's tomcat packages: don't. You just get a silent 400 Bad request error on the holding page for no reason. Download it from upstream, and use that directly. It's very poorly documented, sadly, so to get started:

1. Install the Sun JRE and set $JAVA_HOME appropriately - gcj is ... lacking
2. Grab the Tomcat 'core' tarball and unpack it in place
3. edit conf/tomcat-users.xml to add a user that has the 'manager' role
4. start Tomcat with ./bin/startup.sh
5. Go to http://yourhost:8080/ and log in to "status" with the manager user you added
6. This will list any of the apps you installed (by dumping their .war file in webapps/)

I also set up a virtual host with Apache (for OpenGrok) like this:

<VirtualHost *.80>
ServerName grok.example.org
ProxyPreserveHost On
ProxyPass / http://example.org:8080/
ProxyPassReverse / http://example.org:8080/
</VirtualHost>

Gas no gas abadie pizza please

Well this makes no sense:

Me: "Hi, your letter said I needed to arrange a visit with you to check the gas safety of my flat."
Them: "That's right, what's your details?"
*gives them*
Me: "There's no gas supply in the building, but apparently you have to come see that in person yourselves."
Them: "Yes, that's true. .... OK, we'll send you a letter with the appointment details."
Me: "Uh, I can't just do any time, it needs to be arranged."
Them: "That's OK - if you can't make the appointment on the letter, then you can ring us up after you receive it and tell us."
Me: "..."

Holocaust deniers

Somewhat unpleasantly, I'm a vague acquaintance of a couple of holocaust deniers (in the sense that I've been in the same place as them once or twice). Really weird people:

1. They always bring it up at parties. Seriously, what? If I were a terrorism expert, I'd tend to keep off the subject at parties, since people might see it as a little sensitive. Even if I was just a huge fan of He-Man or something I'd probably only mention it if we were talking about 1980s kids' TV. Why do they always start talking about it?
2. It's never a slight correction. It's always some ridiculous figure they claim, like "zero" or "thousands". Surely if the figures are really dubious, they're not going to be 6 million off? It's equivalent to claiming that nobody lives in Libya.
3. They appear to believe in either the most expertly executed hoax of all time, and their only apparent response to this is to moan about it to people they don't know. How does that make any sense?